According to recent studies, it has been proven that two kinds of cells, regulatory T (Treg) cells and T helper 17 (TH17) cells, which belong to CD4+ T lymphocytes, play important role in autoimmune diseases. These two cells have been known to differentiate from common precursor cells, i.e., näive CD4+ T cells under the influence of a cytokine, a transforming growth factor beta 1 (TGFβ1) (Bettelli, E., Nature, 441: 235-238, 2006). However, Treg cells inhibit the function of abnormally activated immune cells and play important role in immunological tolerance, and TH17 cells, which are inflammatory T cells expressing IL-17, accelerate progress of the autoimmune diseases by maximizing signals of inflammation reaction.
Therefore, the development of therapeutic agents aiming the suppression of TH17 cell activity has been given attention for treating autoimmune diseases not regulated by Treg cells.
US20130071409A discloses a therapeutic agent for treating autoimmune diseases through the regulation of TH17 cells using ICOS (inducible costimulatory, CD278). US20130035333A relates to use of cinnabarinic acid as a modulator of immune responses in autoimmune disorders and discloses a method of treating through the regulation of aryl hydrocarbon receptor activity.
However, it is needed to develop a therapeutic agent for treating disorders related to immune response and inflammation based on the regulation of differentiation of CD4+ T cells into Treg cells and the stabilization of the differentiated Treg cells considering the roles of Treg cells and TH17 cells during the development of the immune system.